The need for moisture barriers for protecting wood from damage in building structures, particularly in flooring systems, is appreciated in the construction and renovation of buildings. One potential problem caused by excessive moisture emission is the lifting and/or separating of the finish floor from the substrate, for example by bubbling, peeling or delaminating. When this happens, a costly replacement of finish flooring becomes necessary to avoid further deterioration, or unsightliness.
Various sources of moisture, such as ground water and moisture from incompletely cured concrete, are known to influence and possibly damage flooring systems. Many polymer-based or polymer-enhanced moisture barriers are known and utilized for abating the negative effects, but moisture persists as a cause of damage to structural components of buildings. Moisture barriers are also known as water, vapor, and condensation barriers.
Epoxy sealers polymer-based compositions customarily used to provide a protective film that adheres to an upper exterior of a concrete substrate. For example, water-borne epoxy moisture vapor treatments, such as SIKAFLOORS® Fast Track Primer (“FTP”) (Sika Corp., Lyndhurst, N.J.), are utilized for preventing moisture damage to toppings and finish floor surfaces from seepage or emission (water, moisture or vapor) through a concrete subfloor. SIKAFLOOR® FTP concrete primer was originally developed by Valspar Federated Flooring Division as a moisture mitigation system for concrete subfloors where the moisture vapor emission rate is between 3 lb/1,000 ft2 (0.01 kg/m2)-8 lb/1,000 ft2 (0.04 kg/m2) per 24 hrs. This product is designed specifically for application to concrete subfloors as a water vapor treatment material that will then be over-layed, possibly by epoxy or urethane coatings, underlayments and floor coverings. Older concrete floors must be shot-blasted to open the surface to allow penetration of the FTP. Under adverse conditions, it is likely that a topical film, such as that formed by an epoxy or non-breathing floor covering, will peel, bubble and detach from the surface, becoming a “floating layer”, which can lead to more problems with adhesive application and finish floor installation.
Cementitious underlayments are desirably used for leveling an uneven subfloor before installing a finished flooring material such as ceramic tile, hard wood, vinyl or wood laminate, as known in the art. However, most conventional cementitious underlayments cannot be used with wood subfloors. One class of cementitious underlayments are non-gypsum materials such as Portland cement—or High Alumina Cement—based materials, and they may require shot blasting because of their propensity to shrink during the curing cycle. Gypsum based pourable underlayments, however, are gaining popularity. The pourable underlayment involves an uncomplicated installation process that includes pouring and spreading gypsum based cement that is mixed on the job site with sand and water until a pourable slurry is obtained. Such a cement is also known as gypsum concrete. The slurry is poured in place and screeded to the desired thickness and smoothness. The gypsum concrete sets and becomes a usable, walkable surface within hours. However, excess water is still present and may take days or weeks to be released from the gypsum cement based underlayment, depending on pour depth and drying conditions.
One of the benefits of a gypsum concrete floor is its resistance to cracking. Gypsum concrete will expand slightly as it goes through the setting and drying process. However, when the flooring substrate is wood, such as dry wood which is commonly found in buildings being renovated, this crack resistance may be compromised because moisture may be wicked away from the gypsum underlayment during the application stage and absorbed into the wood, causing the wood to swell. Because gypsum concrete is not a structural material, the differential movement due to the swelling results in stresses which may cause cracking of the underlayment. Cracks that appear in the underlayment may telegraph through and cause imperfections in the finished floor.
LEVELROCK® pourable underlayment is a pourable gypsum based and self-leveling underlayment commonly utilized between a wood or cement subfloor and a variety of finished floor overlays. As this underlayment sets and dries, excess moisture or “free water” which is that amount of water beyond what is used in the chemical reaction that is the setting process is released. This free water which is required to allow the underlayment to flow properly can be absorbed into the subfloor materials, especially dry wood that is common in aged buildings being renovated. When this absorption occurs, the substrate (subfloor) will swell as the underlayment is hardening and setting in place. The undesirable result is that the underlayment may crack as the subfloor swells and moves at a different rate than the gypsum underlayment. Moisture vapor barrier fabrics, such as MOISTOP® vapor barrier (Fortifiber Building Systems Group, Femley, Nev.), have been placed on top of a subfloor before placing an underlayment. However, different jobs or projects may not always allow for use of such fabrics.
Another consideration is that a dry wood subfloor will absorb or “rob” water from the gypsum underlayment, the water that is intended to aid in the flow of the underlayment. When this occurs, the technician responsible for final smoothing of the floor will have difficulty in achieving a smooth underlayment surface. To overcome this problem, the technician will call for the addition of more water to the mix. This addition of water is expected to be above and beyond the underlayment manufacturer's recommendation and can cause a loss of compressive strength. The gypsum crystals become spread out or displaced, for example, by air bubbles left behind after the added water evaporates. The loss of compressive strength compromises the performance or strength of the floor.
Aqueous emulsion polymer mixtures, such as LEVELROCK™ Floor Primer, LEVELROCK™ Concrete Primer, LEVELROCK™ All-Purpose Sealer or DUROCK® Primer-Sealer high solids sealant (United States Gypsum Co., Chicago, Ill.) have been applied as films or layers that sit on the surface of substrates, including concrete, wood and wood structural panels, with the goal of sealing a highly porous surface. Otherwise, an underlayment installed over the subfloor would not be satisfactorily smooth.
A waterborne latex material, such as acrylic, polyvinyl acetate, polyvinyl alcohol, styrene butadiene, and others known in the art, has also been applied as a film or surface layer to cement and wood substrates as an adhesive or a primer for overlay materials. The latex acts as a primer between a substrate and an overlay. When used, this primer allows for little to no surface preparation before applying the overlay, thereby providing efficiencies as described in U.S. Patent Application Publication No. 2010/0062219.
U.S. Pat. No. 6,399,181 discloses formation of a non-skid mat for surfaces such as garage floors that are at risk of becoming slippery when exposed to fluids such as water or oil. A wood substrate is coated with a thermosetting epoxy resin material. The coated wood substrate is further coated, or laid over, with cloth that has been dipped in an epoxy resin and an amine hardener, possibly the same epoxy as that utilized to coat the wood. To this assembly a third coating is applied, to which is added a granular material such as crushed walnut shells. This tri-coated wood substrate forms a base that is dried and then fastened to a conventional rubber mat by conventional attachment means, such as GORILLA GLUE® adhesive to create a non-skid, water-resistant, oil-resistant surface structure.
U.S. Pat. No. 3,795,533 discloses the preservation and strengthening of porous solid objects, including wooden objects, by sequential impregnation with a plurality of solvent mixtures containing concentrations of curable, hydrophobic, polymeric materials, including epoxides. The solvents utilized may be hydrophilic or hydrophobic. Hydrophilic solvents include dimethylsulfoxone, the aliphatic and aromatic alcohols, the ketones, dioxane, or glycol ethyl ether. Suitable hydrophobic solvents include benzene, toluene, xylene, or mixtures of any of these. Selection of the solvent has an effect on the depth to which the treatment will penetrate the pore. Before impregnating the pores with the polymer composition, the surface of the porous solid to be treated may first be washed by conventional means to remove gross contaminants. The porous solid is then treated sequentially with water-solvent mixtures of increasing solvent concentration. The final treatment is with the solvent alone, to prepare the solid for further impregnation with the polymer-solvent solution. This is a cleaning treatment that removes any water-soluble impurities or any residual water moisture from the pores, and further permits the subsequently applied polymer to be synergistically penetrated deeper into the pore system. Impregnation of the polymeric material after the solvent treatment enables the polymeric material to penetrate as deeply as the capability of the absolute solvent to enter the pore space. In pores of less than one micron in size, when using acetone as the solvent, penetration of the solvent to a depth of about one inch is possible after about ¾ of an hour. Following the cleaning, this method teaches sequential application of curable polymeric compositions of varying/increasing polymeric material concentrations. While the process of first cleaning the pores with solvent is not required, it is recommended to aid the deeper penetration of polymeric compound. One to ten sequential polymeric material applications are recommended, but if only one polymeric treatment is applied, it must be preceded by at least one solvent/cleaning treatment as described above.
The recommended practice for applying FTP sealer to concrete floors is to shot-blast or scurify the concrete floor prior to application of the FTP sealer. This is typically done in almost all concrete surfaces to remove any densifiers or a concrete curing agents that would affect the performance of the FTP sealer and to open up the pores of the concrete surface. The exception to this is a fresh concrete surface that is less than forty-eight (48) hours old.